Wednesday, June 6, 2012

New York’s mayor Michael Bloomberg announced last week that he is going to ban serving sodaor other sweet beverages in large sizes in New York City. The order would limit servings to no more than 16 ounces, basically wiping out the Big Gulp and its super-size friends. It would not affect the sale of big bottles of soda in grocery stores, but would limit consumption in movie theaters, ball parks, and so forth.

Bloomberg is not asking for a new law – since it might not pass, given that a NY1-Marist poll finds that about half of New Yorkers oppose the idea. Instead, he will make it an executive order, which needs only a go-ahead from the city’s eleven-person Board of Health — all appointed by the mayor. And the courts aren’t likely to find it onerous or unjust – since if a New Yorker really, really wants to drink 32 ounces of, say, Mountain Dew all at once, she can just buy two 16-ounce cups.

It’s true that Americans drink a lot of soda. As of 2000, it was estimated that 15% of the average American diet comprised added sugars (i.e., not naturally occurring in foods, like the fructose in apples) – and that about half of the added sugar came from soft drinks. And it’s also true that Americans are heavier now than a generation ago.

So the NYC super-size-soda ban (shall we call it the SSSBan?) is pitched as a public health victory. For instance, Barry Popkin, a professor of nutrition at the UNC-Chapel Hill School of Public Health and a longstanding anti-obesity crusader, says that “controlling sugary beverage portions sizes is critical for reducing weight gain and [the] risks of diabetes in the U.S.”

And Ellen Rautenberg, CEO of Public Health Solutions (a private, nonprofit research firm associated with the NYC Department of Health) points out that limiting portion size is “…one important approach to this multifaceted problem [i.e., obesity] and applying this to sugary drinks, particularly those with no nutritional value, is an excellent place to begin. We went from happily accepting bottles of soda that were 6.5 fluid ounces and have now come to expect that a “regular” drink is 32 ounces.”

(I’m not sure Rautenberg is right that most people think of a quart as a regular-sized portion of soda. But she makes the point about the need for adjusting the landscape of consumption, if we want people to be slimmer.)

And Walter Willett, chair of the nutrition department at the Harvard School of Public Health, says that “New York City’s plan to limit the serving size of soda and other sugar-sweetened beverages sold in restaurants is well-justified by solid evidence. High intakes of these beverages increase the risks of obesity and diabetes and are clearly unsafe for anyone.”

There’s a big problem with the public health argument for the SSSBan, though: it’s probably false.

First, a comprehensive meta-analysis published in 2008 in the American Journal of Clinical Nutrition summarized studies examining consumption of sugar-sweetened beverages in relation to childhood obesity — and found no relationship of sugary-beverage consumption with body mass index.

Willett and his Harvard colleague Frank Hu did their own meta-analysis of studies relating sugary-beverage consumption in children, reporting (Am J Clin Nutr, Jan. 2009) that the average kid who adds one 12-ounce soda to his diet every day would gain 29 kg (64 lbs) per year compared to the same-sized child who does not. But the Willett and Hu results were based only on studies that failed to adjust for total dietary intake. Doing a good analysis of bad science (even at Harvard) doesn’t make the results any more valid.

At the very least, there’s reason to question whether it’s soda that makes obese children obese, or general caloric intake, or lack of exercise, or a combination of all of those.

Second, even if the evidence that soda consumption is associated with weight gain is correct, there has never been evidence that limiting soda consumption to 16 ounces (as opposed to 8 ounces, or 6 ounces, or zero!) can prevent or undo obesity.

Third, if soda is a public health enemy, as Popkin and Willett imply, then it’s hard to see how anything is to be gained by getting McDonald’s to sell sodas only in smaller sizes while large bottles are still available in the supermarket or the bodega down the block.

So here are some questions to think about:

Is the proposed SSSBan just a publicity ploy? Or, as Mayor Bloomberg insists, is it a small step in the right direction?

If soda is really toxic, should it be banned outright? If it’s not banned outright, should it be like alcohol — sold only to adults, and only if they haven’t already had too much?

Everyone agrees that government should protect the public’s health – where would we be without a supply of clean water, or sewage disposal, or air-pollution controls? But should government be in the business of nudging us toward better, healthier behavior?

So far, the SSSBan is only planned for NYC. But it could go further. How should you decide if it’s the right thing for your community?

Philip Alcabes is a professor in the Adelphi University School of Nursing and director of the Public Health Program. He is an epidemiologist and has studied the history, ethics, and policy of public health.